1. Field of the Invention
The present invention relates in general to a control method and apparatus for supporting hard disk and CD-ROM drives through a Personal Computer Memory Card International Association (PCMCIA) interface in a computer system.
2. Technical Background
Hard disk drives, as well as CD-ROM drives, are widely used as storage devices for programs and data in personal computer systems. The reduction in the cost of these mass-storage devices, together with the wide-spread use of a variety of software programs that require ever and ever larger storage space, has turned these storage devices into personal computer standard equipment. In particular, the widely accepted CD-ROM drive not only has become standard in a large portion of desktop systems now being shipped, but also demonstrated the necessity that portable personal computer systems be equipped with the ability to interface to the CD-ROM drives.
A typical interface for the hard disk and CD-ROM drives in the popular personal computer system, specifically, the interface for these drives in the IBM-compatible computer systems, desktop and portable systems inclusive, is the so-called ATA, Advanced Technology Attachment interface. A normal ATA interface supports up to four hard disk and/or CD-ROM drives, provided the drives comply with the specification of that interface. The ATA interface has a 40-pin connector, connecting the hard disk and/or CD-ROM drive devices to the interface electronics circuitry that is normally built into the computer system. In the case of desktop computer systems, the ATA interface is typically implemented in an interface adapter card that resides in a slot on the expansion bus of the computer system, either Industry Standard Architecture (ISA) Video Electronics Standards Association (VESA) or Peripheral Component Interconnect (PCI) bus.
A user upgrading a desktop computer by adding an additional hard disk and/or a CD-ROM drive can perform the upgrade without too much difficulty. On the other hand, however, upgrading a portable computer system, and in particular, the ever popular notebook class of computer, is much more difficult, if not impossible, to upgrade. Most of these computers have severe limitations on the internal adoption of an additional hard disk and/or a CD-ROM drive, due to the obvious restriction of free space inside such computers. Typical notebook computers have one internal hard disk drive, which employs a small diameter platter for its storage disk (typically in the range of 2.5 to 3.5-inch size factors). However, the popular CD-ROM drive devices has a disk diameter of 12 cm, which makes it too bulky to be built into most notebook computers, although not impossible.
To solve the problem of interfacing a notebook computer to an additional hard disk and/or to a CD-ROM drive, a connector for the ATA or, ISA bus of the notebook computer can be provided for the computer to be interfaced to the external hard disk and/or CD-ROM drives that comply with the ATA standard. However, there is no standard mechanical specification for the ISA bus for notebook computers that all CD-ROM drive manufacturers can readily adopt. The result of this lack of standardized ISA bus mechanical specification for notebook computers is the emergence of proprietary docking stations that provide for the hard disk and/or CD-ROM drive expansion capability for notebook computers. However, these proprietary interfacing connections limit the numbers of sources which consumers have for the selection of an expansion hard disk and/or a CD-ROM drive, and, as a result, such expansion devices for the notebook class of computer systems are unnecessarily expensive.
There is one expansion interface standard for notebook class computers that is widely accepted by notebook computer manufacturers. This is the PCMCIA (Personal computer Memory Card International Association) interface. As the name implies, the PCMCIA interface was originally proposed for the expansion of memory storage for small pocket/portable computers.
To utilize this standardized PCMCIA electronic interface, which is found on almost every notebook computer now being manufactured, as an expansion interface for a hard disk and/or a CD-ROM drive for notebook computers, an electronic conversion device was proposed and built for the conversion between the ATA and the PCMCIA buses. FIG. 1 depicts such an implementation.
As is shown in FIG. 1, the conventional scheme of providing a conversion between the ATA interface 30 and the PCMCIA interface 10 requires building a PCMCIA/ATA conversion integrated circuit electronic device 20 that actually performs the conversion for the electronic signals between the two interface standards.
This conversion IC device 20 can be implemented in one single IC chip, so that it can be fitted within the small dimension of a PCMCIA card that can be inserted in a PCMCIA slot of a notebook computer. The added hard disk and/or CD-ROM device can be attached to the ATA connector of the device 20, allowing the hard disk and/or CD-ROM drives to be physically hooked up to the notebook computer externally.
However, this scheme of interfacing the hard disk and/or CD-ROM drive to a computer system has several drawbacks. First of all, conversion device 20 represents an added cost for the disk expansion device. Second, since the expansion drives, either a hard disk or a CD-ROM, appear to the computer system as PCMCIA devices, special software driver routines are required for such drive expansion. Thus, using a hard disk and/or a CD-ROM drive in an IBM-compatible computer system as a PCMCIA device presents additional software compatibility problems.